Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds value by specifying the exact types of data read (terms, verification status, source evidence, carrier links), which goes beyond the generic title. However, it does not disclose any other behaviors such as error handling, rate limits, or authentication requirements, which would be expected even with annotations present.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, front-loaded sentence that states the verb and resource immediately. It avoids any fluff or repetition, with each word contributing to the meaning. No unnecessary details are included, making it highly efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's simplicity (one parameter, output schema provided, annotations cover safety), the description covers the core purpose and data returned. However, it lacks explicit usage guidance (when to use over siblings) and does not mention any prerequisites or expected behavior beyond the read operation. This leaves an agent without clear selection criteria, so completeness is only partially met.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 0% description coverage for parameters, so the description must compensate. The description implies that plan_id identifies a plan by saying 'a plan's details', which gives basic semantic meaning. However, it does not elaborate on the format, constraints, or potential edge cases (e.g., invalid ID behavior), so the compensation is minimal but sufficient for a single simple integer parameter.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses the specific verb 'Read' and resource 'a plan's terms, verification status, source evidence and carrier links', clearly defining the tool's function. It distinguishes itself from siblings like search_plans (which searches) and compare_plan_costs (which compares) by stating it retrieves detailed plan-specific data, not a list or comparison.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no explicit guidance on when to use this tool versus alternatives. It does not mention that this is the right tool for retrieving full details of a specific plan, nor does it exclude using it in contexts where siblings might be more appropriate. The 'Read' verb implies it is for detail retrieval, but there is no direct comparison to siblings like search_plans or get_switching_guide.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.